Electrodeposition of silver from the system AgNO 3—ethyleneglycol—water. Effect of temperature ( ∼ −30°C) on the smoothness of silver deposits

Abstract

The electrodeposition of silver from a nitrate bath can be improved by lowering the temperature and by the addition of ethyleneglycol as anti-freeze. When the bath temperature is lowered below 0°C, the dendritic silver deposition is suppressed and a smooth surface is obtained; at −30°C a very finegrained deposit results. The dendritic growth is supposedly prohibited partly by the lowering of temperature and to a less extent by the adsorption of ethyleneglycol at the surface both of which might enhance the activation overvoltage of silver deposition. From the polarisation measurement in, 0·25 M AgNO 3 electrolytes, the exchange current density of Ag deposition was evaluated as 1·70 × 10 −2 A/cm 2(25°C) and with 50 vol. per cent ethyleneglycol, 9·72 × 10 −4 A/cm 2 (25°C) and 1·22 × 10 −5 A/cm 2 (−32°C). Adsorption of ethyleneglycol on Ag cathode was discussed by differential capacitance change.